Racial differences in sarcoidosis incidence: a 5-year study in a health maintenance organization

Reports of racial differences in the incidence of sarcoidosis, a granulomatous disorder of unknown etiology, are primarily based on studies of military and veteran populations. To determine racial differences in sarcoidosis incidence in a metropolitan population the authors conducted a study of newly diagnosed cases that occurred between 1990 and 1994 among members of the Health Alliance Plan health maintenance organization in Detroit, Michigan. The study population was racially heterogeneous, was limited to individuals aged 20-69 years, and comprised about 5% of the Detroit metropolitan area population in that age group. Annual age-adjusted incidence, in number of new cases per 100,000, was highest in African-American females (39.1 cases). The next highest incidence was found in African-American males (29.8 cases), followed by Caucasian females (12.1) and Caucasian males (9.6). African-American females aged 30-39 years were at the greatest risk, with an annual incidence of 107/100,000. Overall, African Americans had about a threefold higher age-adjusted annual incidence (35.5/100,000) compared with Caucasians (10.9/100,000). Additional adjustment for sex, area of residence, and year of study resulted in 3.8-fold greater risk for African Americans compared with Caucasians. This study further confirmed the higher incidence of sarcoidosis in African Americans compared with Caucasians, but the racial difference was lower than previously reported. The results should be more generalizable than previous studies done with select populations and should serve as a useful frame of reference for future epidemiologic research of sarcoidosis.